1. Wednesday, Jan 21, 1:30 to 3:10 pm, Session 15 : Image/Video Transmission I (First Talk, Other topics deal with error-resilience and error-concealment)

2. Limitations of traditional error-resilience methods
Broadcasting+FEC+PET+FEP
FEC (“Cliff” effect)
Layered Coding with Priority Encoding Transmission (PET)
(Inferior R-D Performance)
[Albanese et al., 1996]

3. Outline Systematic source-channel coding framework
Lossy Forward Error Protection using Wyner-Ziv coding
Results and Conclusions
The audience will need a little intro on WZ coding. No equations, just the idea.

4. Wyner-Ziv coding background
Side-info at encoder and decoder:
encoder
decoder X X’ Y
encoder
decoder X X’ Y
Side-info at decoder only:
[Wyner and Ziv, ]
Can achieve bit-rate savings due to correlation between X and Y

5. Systematic Source-Channel Coding
Wyner-Ziv
Encoder
Side
info
Digital
Channel
Analog
Decoder
[Shamai, Verdu and Zamir, 1998]
Enhancing analog transmission systems using digital side information [Pradhan and Ramchandran, 2001]
Robust predictive coding [Sehgal and Ahuja, 2003]
Lossy source-channel coding of video waveforms
[Aaron, Rane and Girod, 2003]
Channels A and D+WZ relation+Pradhan+Sehgal

6. MPEG Decoder with Error Concealment
Systematic lossy forward error protection
MPEG Encoder
MPEG Decoder with Error Concealment S S’
Side information
Error-Prone channel
Slepian-Wolf Encoder
Slepian-Wolf Decoder
Reconstruction
Coarse Quantizer S*
Wyner-Ziv Encoder
Wyner-Ziv Decoder
Conventional encoded+decoded+WZ representation (explain later)+decoding+lossy (clear later)
Systematic source-channel coding
“Lossy” protection
Fully backward compatible with legacy systems

7. Fallback Scheme for error-resilienceT
T-1
Q-1 Q MC EC
Main
Encoder - S +
Channel ED
T-1
Q-1 + MC S* + T
T-1 q
q-1 MC EC
Fallback
Encoder -
T-1
q-1 ED + MC
Fallback when
errors occur
say lossy

8. Proposed Wyner-Ziv codec
Video
Encoder
main S
Channel ED
T-1
Q-1 + MC S*
T-1
q-1 ED + MC
Side
information
Video
Encoder
“coarse”
Reconstructed
frame at
Encoder
Video
“coarse”
R-S
Decoder
R-S
Encoder
Conventional+fallback+generate side info+send only parity+reason for lossy
Transmit only
parity symbols
Wyner-Ziv encoder
Wyner-Ziv decoder

9. Transmit along this direction
Reed-Solomon codes across slices
Transmit along this direction k n X X
row/block+filler+n,k explanation+erasure+anim play
RS code across slices
1 byte in slice
filler byte
Erasure Decoding
parity byte

10. Simulation setup Codecs: Main Codec  H.26L (JM2.0) codec
WZ Codec  H.26L codec and R-S codec.
Settings:
1 Slice = 11 macroblocks = 1/2 GOB for CIF frame
Identical slice structure for main and WZ stream

11. Results (1) Foreman.CIF Main stream @ 1.092 Mbps FEC (n,k) = (40,36)
FEC bitrate = 120 Kbps
Total = 1.2 Mbps
Coarse stream @ 270 Kbps
FEP (n,k) = (52,36)
WZ bitrate = 120 Kbps
Foreman bitrate+FEC bitrate+FEP bitrate+larger range+error concealment versus quantization

12. Results (2) Visual Comparison
Foreman 50 CIF symbol error rate = 4 x 10-4
With FEC
1.092 Mbps kbps
(38.32 dB)
With FEP
1.092 Mbps kbps
(38.78 dB)

13. Results (3) Visual Comparison
Foreman 50 CIF symbol error rate = 10-3
Quantization artifacts invisible
With FEC
1.092 Mbps kbps
(33.03 dB)
With FEP
1.092 Mbps kbps
(38.40 dB)

14. Results (2) Coastguard.CIF
Main Mbps
FEC (n,k) = (40,36)
FEC bitrate = Kbps
Total = 3.5 Mbps
Coarse 1 Mbps
FEP (n.k) = (44,36)
WZ bitrate = 220 Kbps
Total = 3.4 Mbps
Coarse 658 Kbps
FEP (n.k) = (48,36)
Add the third curve here, as presented in the paper (Important).

15. MPEG Decoder with Error Concealment
Ongoing Work : Embedded WZ codec
MPEG
Encoder
MPEG Decoder with Error Concealment S S’ S*
Wyner-Ziv
Encoder A
Decoder A
S**
Wyner-Ziv
Encoder B
Decoder B
Error-Prone channel
Graceful degradation of video quality
Does not require layered representation of original video signal

16. Conclusions
Systematic lossy forward error protection scheme for error-
resilient digital video broadcasting
Outperforms conventional FEC schemes, when SER increases
Fully backward compatible with legacy broadcast systems
Can construct embedded Wyner-Ziv codec which achieves
graceful degradation without layered representation.